85811021 has 2 divisors, whose sum is σ = 85811022. Its totient is φ = 85811020.

The previous prime is 85811017. The next prime is 85811023. The reversal of 85811021 is 12011858.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70795396 + 15015625 = 8414^2 + 3875^2 .

It is a cyclic number.

It is not a de Polignac number, because 85811021 - 2² = 85811017 is a prime.

It is a Sophie Germain prime.

Together with 85811023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (85811023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42905510 + 42905511.

It is an arithmetic number, because the mean of its divisors is an integer number (42905511).

Almost surely, 2^85811021 is an apocalyptic number.

It is an amenable number.

85811021 is a deficient number, since it is larger than the sum of its proper divisors (1).

85811021 is an equidigital number, since it uses as much as digits as its factorization.

85811021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 85811021 is about 9263.4238270739. The cubic root of 85811021 is about 441.0769435351.

Adding to 85811021 its reverse (12011858), we get a palindrome (97822879).

The spelling of 85811021 in words is "eighty-five million, eight hundred eleven thousand, twenty-one".